Seven years ago scientists discovered the unpoetically named ocean bacterium ANME-1, the first organism found to feed on methane.

Now researchers are learning more about how that bacterium and similar organisms behave and influence Earth's methane cycle.

Writing in tomorrow's issue of the journal Nature, the team describes three communities of methane-munching microbes found on an Arctic undersea mud volcano in the Barents Sea above western Russia (Russia map).

These creatures include bacteria, worms, and a previously unknown species from the archaea group of single-celled life-forms. Each creature has an uncommon metabolism that depends on the energy stored in methane, and each processes the gas in a unique way.

While the creatures' specific biochemistries remain unclear, one microbe uses oxygen to break down methane. Another teams up with unrelated bacteria species and uses sulfate to convert the greenhouse gas into energy.

Methane Filters

Thanks to the microbes, a significant portion of the methane belched from deep below the seafloor by the Haakon Mosby Mud Volcano, for example, never reaches the ocean.

That's good news for many-celled landlubbers worried about global warming. Atmospheric methane is nearly 20 times more powerful than carbon dioxide when it comes to trapping heat from the sun.

"Methane-consuming microorganisms are critical to maintaining a healthy climate on Earth," said study co-author Antje Boetius, a microbiologist at the Max Planck Institute for Marine Microbiology in Bremen, Germany.